US1911890A

US1911890A - Grinding machine

Info

Publication number: US1911890A
Application number: US347097A
Authority: US
Inventors: Warren F Fraser
Original assignee: Norton Co
Current assignee: Saint Gobain Abrasives Inc
Priority date: 1929-03-14
Filing date: 1929-03-14
Publication date: 1933-05-30
Anticipated expiration: 1950-05-30

Description

May 30, 1933. FRASER 1,911,890

GRINDING MACHINE Filed March 14, 1929 3 Sheets-Sheet l 15' 6 Fig. 2

I gwuwntoz WITNESSES 7 WARREN F. FHHSEfi W H. M I W W W.

May 30, 1933.

w. F. FRASER GRINDING MACHINE Filed March 14, 1929 3 Sheets -Sheet Fig. 4

Fig. 5

gwuewtoo I MRREN I-T FFrHSER WITNESSES Patented May 30, W33

WARREN F. FRASER, 0F WESTBORO; MASSACHUSETTS, ASSIGNOB- T0 NOETON COMP 4 0F WORCESTER, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS GRINDING MACHINE Application filed March 14, 1929. Serial No. 347,097.

This invention relates to feeding mechanism for machine tools wherein it is desirable to efiect a relative movement of the work and an operating tool at different rates of speed and with extreme accuracy. Whilev certain features of the invention are of general application, it is of particular value as embodied in grinding machines wherein the Work and the grinding element are relative- 1y moved toward and away from each other at different rates in diiferent parts of the machine cycle, Accordingly, the invention will be first disclosed in its application to grinding machines.

Fluid pressure systems have been employed heretofore in connection with the feeding mechanism of grinding machines and such systems are desirable on account of their smooth and continuous action and the simplicity of their mechanical construction. In one aspect, the present invention consists broadly in feeding mechanism including a fluid pressure actuator, a controlling valve for governing the action thereof, and a caliper device operating on the work during the grinding operation to which the controlling valve is responsive.

It is important, to insure the accurate operation of the calipering device, that it should be light in construction and effective in its controlling action under conditions of light pressure. The area of its contact points must be kept small in order to reduce the possibility of foreign matter being retained between them and the work and the pressure must be light to avoid marking the work, especially where it is not hardened. In another aspect, the present invention consists in calipering mechanism of novel construction wherein the calipering movement is utilized to trip a sensitive latch mechanism under conditions of light pressure and the tripping of the latch mechanism is takenadvantage of in a novel manner to govern a controlling valve in the fluid pressure system. As herein shown, the controlling valve is arranged to be positioned initially by the operator and this operation energizes a spring which is subsequently utilized to effect automatically the movement of the valve when tripped by the calipering device. By this construction I have found it possible to maintain adequate flow of fluid under pressure during the grinding operation and yet elfectually cut oft" the flow in response to an extremely slight and delicate movement of the caliper elements.

Other features of the invention relate to novel feeding mechanism of the fluid pressure type, whereby the work and the grinding element may be moved toward and from each other accurately, with adequate power and at speeds appropriate to the difierent requirements. As herein shown, the grindlng wheel is moved at high speed from a remote initial position into a preliminary grinding relation to the Work, then fed in to the work at a slow speed until a predetermined diameter is reached, then held at rest While a final reduction of diameter is edected, and finally retracted at high speed to its initial position.

To accomplish these results, the present invention contemplates feeding mechanism actuated by fluid pressure and a separate fluid pressure system for controlling the rate of feed. It is believed that the principle which this combination of fluid pressure systems involves has not been heretofore employed in controlling the feeding mechanism of grinding machines or other machine tools. It presents the advantages of smoothness of operation without shock or overthrow, reliability, and a wide range of variation as to rate of feed. As herein shown, the separate fluid pressure system referred to includes a passage throu h which fluid under pressure is forced during the in-feeding operation, which passage is provided with an adjusting valve for varying its efiective opening and thus controlling the rate of fluid displacement and, consequently, of the feeding movement. The system also includes mechanism by which it is brought into action at a predetermined point in the feed so that, if desired, the initial feeding movement to establish the grinding relation may take'place at a higher rate of speed independent of the control of the system.

These and other features of the invention will be best understood and appreciated from the following description of a preferred embodiment thereof, selected for purposes of illustration and shown in the accompanying drawings, in which Fig. 1 isa view in perspective showing somewhat diagrammatically the arrangement of the grinding wheel slide and its feedmg mechan1sm, the work and the calipering device;

Fig. 2 is a sectional view of the calipering device on the line 22 of Fig. 8;

Fig. 3 is a sectional view, on the line 33 of Fig. 5, of the hand wheel and associated parts;

Fig. 4 is a sectional view of a portion of the calipering device on the line 44 of Fig. 7;

Fig. 5 is a view in elevation, partly in section, of the feeding mechanism Fig. 6 is a plan view of the calipering device;

Fig. 7 is a view in end elevation of the controlling valve mechanism, partly in section; and

Fig. 8 is a view in elevation of the calipering device with its associated mechanism shown in section.

In the cylindrical grinding machine illustrated, the grinding wheel 100 is mounted on a driven shaft 102 journaled in a cross slide 104 suitably supported and guided by transverse ways in the machine frame. In the bottom of the grinding wheel slide 104 'is a nut 106 which cooperates with the lead screw in a transverse shaft 12 for movin the slide to carry the grinding wheel toward or from the work. The work piece to be ground is illustrated as a shaft 108 supported upon centers, one of which110 is shown in Fig. 1, and arranged to be rotated while being ground. The mechanism thus far described is well known in commercial grinding machines such, for example, as that shown in the patent to Norton No. 1,443,924, grant-- ed Jan. 30, 1923.

To move the grinding wheel 100 toward and from the rotating work, the following mechanism is employed. The lead screw shaft 12 carries a pinion 27 at its forward end which meshes with another pinion 28 on the rear end of a shaft 10 journaled in the machine frame. Rotation is transmitted to the lead screw shaft 12 through the shaft 10, which may be turned manually by a hand wheel 14 fast to its forward end or mechanically and automatically through a pinion 13 which, in turn, is driven by a reciprocatory rack 26. The pinion 13 may be locked to the shaft 10 or may be free to rotate upon it according as it is desired to utilize the automatic feed or the manual feed. To thisend, a gear 15 is secured to the pinion 13, being arranged to turn with it upon the shaft 10 and to mesh with a pinion 24 formed in the.

rear end of a plunger 21 which is slidably mounted in a sleeve 16. The sleeve 16 is slidably keyed to plunger 21 and free to turn with it in the hand wheel 14. It has a radially extending arm carrying a locking pin 17 adapted to enter one of a series of holes 20 arranged circumferentially in a disk secured to the hand wheel 14 and being maintained in locking position by a spring, shown in Fig. 3. The plunger 21 may be retracted, disengaging the pinion 24 from the gear 15, when it is desired to free the hand wheel 14 and the shaft 10 from the automatic feed mechanism.

It is desirable, for purposes which will presently appear, to provide for changing by small amounts the angular relation of the pinion 13 and the shaft 10 and this may be effected by rotating the sleeve 16 and the plunger 21 through the desired angle and looking it in adjusted position, as determined by one or another of the holes 20.

Provision is made for moving the rack 26 at two different speeds in a direction to advance the grinding wheel toward the work and at one speed in the reverse direction. To this end, the rack 26 is provided at either end with downwardly extendir

1g arms

28 and 30 between which extends a piston rod 32. The rod 32 passes through the heads of a fluid pressure cylinder 36 and is provided with a piston 34 by which it is moved in either direction according to which end of the cylinder fluid pressure may be admitted. A pipe 62, connected to the left head of the cylinder, acts as an inlet pipe during the in-feeding movement of the grinding wheel and a pipe 64, connected to the right head of the cylinder, acts as anoutlet pipe at the same time. The functions of these pipes are interchanged during the reverse movement of the grinding wheel.

During a portion of the in-feeding movement of the grinding wheel, the rack 26 travels at high speed without retardation, bringing the grinding wheel from a remote position up to a position closely adjacent to or in preliminary engagement with the work to be ground. When this condition has been reached, further movement in the same direction is continued but at a greatly reduced speed and such motion constitutes the grinding feed. To effect this result, the motion of the rack 26 is retarded. To this end, an auxiliary cylinder 40 is arranged beneath and parallel to the cylinder 36'and is provided with a piston 42 connected to a piston rod 44 extending through the left-hand head of the cylinder 40 and adapted to be engaged at a predetermined point in the travel of the rack 26 by the lower end of the arm 30 which is secured to the rack. The cylinder 40 is normally filled with oil or other fluid and the piston rod is normally moved outwardly toward the left by a compression spring 46 which encircles the piston rod 44 and bears between the collar 45, fast to the piston rod, and the head of the cylinder. The right-hand head 38 of the cylinder is provided with an outlet port communicating with a valve member 50 having an outlet passage controlled in size by a needle valve 52 and a by-pass normally closed by a check valve 54. 0th passages communicate with a pipe 56 leading to an oil reservoir 58 arranged somewhat above the level or the cylinder 40. It will be understood that the high speed movement of the rack 26 toward the right (Figs. 1 and 5) is terminated when the arm engages the end of the piston rod 44. Further movement of the rack 26 is effected against the resistance of the oil confined between the piston 42 and the small adjustable outlet controlled by the needle valve 52. Only as oil escapes through this passage can the piston 42 move and the rate of I travel of the rack 26 is, accordingly, reduced to the speed determined by the setting of the needle valve.

When the grinding feed movement and the final grinding have both been completed and the piston 34 is moved toward the left by reversing the direction of fluid pressure within the cylinder 36, as will be presntly explained, the spring 46 is efiective to move the piston 42 toward the left and the check valve 54 will open, permitting the oil which has been displaced at a slow rate to the reservoir 58 now to return rapidly and follow the piston 42.

The mechanism for controlling the admission of fluid pressure to the cylinder 36 will now be described. In certain phases this is controlled by the action of a caliper device, shown in Figs. 2 and 8/ Ways 130 are provided in the machine frame for supporting the caliper device, which is mounted upon a bracket 132 shaped to fit the ways and to be clamped in any desired position thereon by a clamping plate 134 which is bolted to the lower side of the bracket. The bracket 132 has a plane upper face and a carrier member 136' pivotally mounted at its lower end upon a pin 138. Pivotally mounted by a pin 139 in the upper end of the carrier member is a frame piece 140 which carries two forwardly extending

bars

142 and 144. The bar 144 is provided with a boss in which is mounted a spring plunger 146 which bears upon the plane upper face of the bracket 132 and urges the

bars

142 and 144 and the parts carried thereby upwardly to a position determined by the-engagement of the lower caliper member with the bottom of the work. The plunger 146 is provided at its upper end with a stop nut which serves to limit the downward movement of the plunger and, consequently, the upward movement of the caliper bars when no work is engaged by the lower caliper member. The

bars

142 and 144 are riveted together by rivets 148 and these extend through the upper end of a downwardly curved bracket member 150. A horizontally disposed stop screw 152 projects through the bracket member 150 and is arranged to engage the work piece at a point substantially opposite the grinding point and to locate transversely the calipering device. .The bracket member also carries at its lower end an upwardly extending contact screw 156 which is designed to engage the bottom of the work piece, being pressed against it by the action of the spring plunger 146.

Between the

bars

142 and 144 and above the bracket member 150 is pivotally mounted a rocker bar 160 upon a transverse pin 162. At its forward end the rocker bar carries a contact screw 164 arranged to engage the upper side of the work piece. The pin 162 .is provided with flanged bushings and surrounded by a sleeve 17 O in itsenlar ged intermediate portion. The sleeve ,170 has an opening through which passes the lower end of a locking pin 172 threaded .into the rocker bar 160 and adapted to engage a fiat formed in the pin 162 and to retain it against endwise displacement.

Journalled on the sleeve 170 and flush with the sides of the rocker bar. 160 is a forked beam 180, the two branches of which are shown in section in Fig. 2. In the rear end of the rocker bar 160 is provided an adjusting screw 184 which is adapted to bear at its lower end upon a transverse web 182 in the forked beam 180. The adjusting screw is provided with a graduated knurled head cooperating with a spring detcnt to maintain the screw in all positions of adjustment. The

rocker bar 160 and the forked beam 180 constitute in sheet a single two-part rocker, the arms of which may be relatively adjusted by turning the adjusting screw 184. A hairpin spring 188, located between the forks of the beam 180, serves to maintain the end of the adjusting screw 184 always in engagement with the web 182. A leaf spring190, mounted between the

bars

142 and 144 and bearing upon the web 182 near its lower end, serves to counterbalance the compound beam and maintain the contactscrew 164 in engagement with the upper surface of the work piece. By turnin the adjusting screw 184 downwardly, the rorward end of the rocker bar 160 is lowered and contact screw 164 brought closer to the contact screw 156, thus aflording convenient means for making an adjustment for determining the point at which the caliper acts in controlling the grinding.

The fluid pressure controlling valves, which are controlled by the beam 180 as its outer end moves upwardly, will now be described. The rear end of'the beam 180, which is periorated for the sake of lightness, extends into a housing 191 where it is provided with a transverse extension 192' at either side carrying an adjustable contact screw 194. Each contact screw 194 is arranged in vertical alignment with and beneath a tripping pawl 196 pivotally mounted in the casing 191. and cooperating'at its free end with a single tooth ratchet disk 198 fast on a transverse shaft 200 journaled in the casing and carrying a pinion 204 at its outer end, see Fig. 4. Each pinion 204 meshes with a gear 206 on a transverse shaft journaled at the rear of the shaft 200 and having an elongated pinion 208. Each pinion 208 meshes with a rack formed in a vertically disposed rod 210 and each rod extends upwardly through the cover of the casing, where it is provided with a knob by which it may be moved manually in one direction, that is to say, downwardly.

Beneath the casing 191 and secured to the frame piece 140 is a valve block or body 212 having two vertical cylindrical bores therein to receive ground sleeves 214, each constituting a valve cylinder. The lower end of each valve cylinder 214 is closed by a head 220 and a valve plunger 216 is arranged for vertical movement within each cylinder. A. compression spring 218 interposed between the bottom of the valve plunger and the head 220 tends to move the valve plunger at all times upwardly into the dotted line position shown in Fig. 7. Each valve lunger 216 is eirtended through the upper ead' of its cylinder and engages with the lower end of one of the rods 210 by which it may be manually depressed against the action ofthe spring 218.

Each valve plunger has a centrally disposed reduced portion and two heads which fill the bore of its cylinder. Fluid pressure is supplied to the inlet port 222 of the lefthandvalve by an inlet pipe whichmay extend to any source of fluid pressure, such as an air compressor or accumulator. en the valves occupy the position shown in Fig. 7, which they do when they have been manually depressed, fiuid under pressure passes through the left-hand valve to the port 224 and thence to the pipe 62 with which it communicates. The piston 34 in the cylinder 36, therefore, travels toward the right and fluid under pressure is exhausted, through the pipe 64 communicating with the port 226 of the right-hand valve and from thence, through the valve, to the exhaust port 228, where it escapes 'to the atmosphere.

The valves remain in position shown in Fig. 7 during the preliminary in-feeding movement of the grinding wheel and during the slow grinding feed thereof. The termination of the grinding feed is determined by the action of the caliper device when the work has been reduced to a predetermined diameter that will permit the left-hand pawl 196 to be tripped from the ratchet tooth of the disk 198. When this occurs, the lefthand valve is immediately moved to the dotted line position, shown in Fig. 7 and the inlet'port 222 is closed, holding the piston 34stationary and maintaining the grinding wheel at rest. The grinding operation continues under these conditions until all strains it i the mechanism have been dissipated and the resulting slight further reduction in the diameter of the work has occurred. When this point is reached, the slight additional movement imparted to the beam 180 is sulficient to release the right-hand pawl 196, permitting the right-hand controlling valve to move to the dotted line position shown in Fig. 7. Under these conditions fluid under pressure supplied by the pipe 60 passes through the internal passage 230 which extends in the valve body between the port 222 and a port 232 of the right-hand controlling valve. From this port fluid pressure enters the right-hand valve and reaches the port 226, whence it passes to the pipe 64 and is admitted to the right end of the cylinder 36, forcing the plunger 34 toward the left and moving the grinding wheel rapidly away from the work. During this part of the cycle, fluid under pressure is exhausted from the cylinder 36 through the pipe 62 and reaches the left-hand valve through the port 224, from whence it passes through the valve andescapes to the atmosphere through the outlet port 225.

Vent ports

227 and 228 are provided at the upper endof the lefthand and right-hand controlling valves respectively to prevent air from being entrapped therein. Y

It will be understood that the caliper device has a double pivot mounting which permits it to move freely up and down and toward and from the work, the pivots being the in 138 and the pin 139 which connects the rame piece 140 with the carrier member. 1

A lever 250 is provided for convenience in manually shifting the caliper device into and out of operative position. The pin 139 is extended out through the frame piece 140 and forms a fulcrum for the lever 250. A link 301 is pivotally connected at one end to the lever 250 by a bolt. The opposite end of the link is slotted, as shown in Fig. 1, and adapted to engage the reduced outer end of a stud set rigidly in the bracket 132. A tension spring normally maintains thisstud in contact with the inner end of the link 301. The portion of the lever 250 adjacent to its fulcrum and the link 301 constitute a toggle mechanism which, in the position shown, is locked; that is, its pivot point lies below the line of the link 301.

lVhen the lever 250 is moved upwardly about its fulcrum point, the toggle is broken and the entire caliper device is moved to an inoperative position away from the work. When the lever 250 is swung in the other direction, the caliper device is moved to operative engagement with the work as determined by its three contact screws. The caliemeeo The operation of the feeding mechanism in

screws

156 and 164 into engagement with the spring connection with the grinding machine above described is as follows. Appropriate preliminary settings are first made in respect to the position of the pinion 13 with reference to the feed shaft 10 to bring the grinding wheel into the desired initial relation to the work piece- 108. The caliper device is moved into operative position opposite the grinding wheel 100 and a preliminary setting is made by turning the contact screws to bring the work at diametrically opposite points and the rocker bar 180 into a position to permit the two disks to be locked by the pawls 196 when the valves 216 are depressed by the operator. When this occurs, the valves occupy the positions shown in Fig. 7, the inlet port 222 being open and fluid under pressure being admitted to the cylinder 36 at its lefthand end. The piston 34 and the rack 26 are, therefore, moved rapidly toward the right and the shaft 10 rotated in a direction to feed the grinding wheel rapidly toward the work. The rapid in-feeding movement is of measured duration and terminates when the arm 30 encounters the end of the contact rod 44, as it is about to do with the parts in the position shown in Fig. 5.

The high speed in-feeding movement is a movement preliminary to the actual grinding and brings the grinding wheel in from the inoperative initial position which it 00- cupies during the insertion of the work to a position in which it is barely in grinding contact with the work. At this point the arm 30' begins to displace the rod 44 and piston 42 toward the right against the tension of the 46 and against the back pressure of the 011 contained in the cylinder 40. Since 3 the fluid pressure against "the piston 34 remains constant, the increased resistance made effective b the piston 42 abruptly reduces the rate of movement of the rack 26 so that the in-feeding movement of the grinding wheel continues at a greatly reduced rate. The oil behind the piston 42 is forced outwardly at a rate determined by the setting of the needle valve 52 and is delivered to the reservoir 58. The 'in-feeding movement continues under these conditions until the caliper device permits the beam 180 to rise sufficiently to trip the left-hand pawl 196 from its associated disk. thereby releasing the lefthand valve 216 and permitting it to move up- 0 wardly' to the position indicated in dotted ing wheel maintained in the position thus determined by the action of the caliper, while a further slight reduction in the diameter of the work is efiected while the machine strains are dissipated and pressure of the grinding wheel against the work relieved. The adjustable contact-screw 194 in the right-hand side of the extension 192 of the beam 180 is set so that the movement of the caliper in response to this final grinding will trip the right-hand pawl 196 and release the righthand valve 216, permitting it to move upwardly and establish communication between the

ports

232 and 226 so that fluid under pressure is now admitted to the right-hand end of the cylinder 36 and the rack 26 is moved in the direction to rotate the shaft 10 for'the reverse feeding movement. This movement takes place at high speed and independently of the separate rate-controlling fluid pressure system because the arm 30 at once moves away from the contact rod 44. As already explained, the piston 42 is returned to initial position by the spring 46, the check valve 54 opening to'permit the fluid from the reservoir 58 to follow the piston. The operator may now release the caliper device from the finished work and insert a new piece of work in readiness for a repetition of the operations just outlined.

It will be noted that the in-feeding movement of the grinding wheel is caused by the setting of the controlling valves 216 by the hand of the operator. The stopping of the grinding feed and the separating of the wheel and the work, on the other hand, are efl'ected by the movement of the valves occurring automatically in accordance with the action of the caliper device. In case it should be desired to rough grind a work piece independently of the caliper device, the operator may depress the rods 210 without positioning the caliper upon the work. This movement of the valves will start the rapid approaching movement of the grinding wheel which will, at the proper time, automatically shift as above described to the slow in-feed and when the wheel has ground away the rough outer surface of the work, the operator may swing the caliper device forward into operative engagement and leave the valves to their automatic control.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a inding machine having a work support an a rotatable grinding wheel, feeding mechanism for the wheel, a fluid pressure cylinder and piston for actuating the mechanism in either direction, a controlling valve, actuating mechanism therefor arranged to be latched under spring tension in a position to admit fluid under pressure to the cylinder to cause an infeed of said mechanism and to cut off fluid when released to stop said infeed, and a caliper device having members engaging the work at diametrically opposite points for tripping said valve actuating mechanism.

2. In a grinding machine, feeding mechanism, a fluid pressure cylinder and piston for actuating said mechanism in either direction, a controlling valve therefor which is biased to a closed position, a gear train operatively connected to move with said valve, means to lock said train to hold the valve in an open position to cause an infeed of said mechanism, a trip acting to release said means to cut off fluid to stop said infeed, and a caliper device engageable with the work and operatively connected to actuate said trip and stop the feeding movement.

3. In a grinding machine, feeding mechanism, a fluid pressure cylinder and piston for actuating said mechanism, a valve for controlling the admission of fluid pressure to said cylinder and its cut-ofl therefrom, a spring tending to move said valve to its cut-off position, a gear train connected to the valve and including a ratchet disk, a'pawl cooperating with said disk .to latch the gear train with the valve in pressure-admitting position, and a caliper device arranged to trip said pawl.

4. In a grinding machine, feeding mechanism, a fluid pressure cylinder and piston for actuating said mechanism, a pair of valves arranged side by side and movable successively to effect a stopping of fluid pressure and a reversal of the direction of pressure in the cylinder, and a caliper device acting to initiate the movement of said valves one after the other.

5. In a grinding machine, feeding mechanism, a fluid pressure cylinder and piston for actuating said mechanism, a pair of valves for controlling the admission of fluid pressure to opposite ends of the cylinder, means independent of said valves for regulating the rate of feed in one direction, and a caliper device to which said valves are successively responsive.

6. In a grinding machine, a grinding wheel slide, a feeding mechanism therefor including a nut and screw connected to move the slide, a fluid pressure system including a piston connected to rotate the feed screw in opposite directions, a stop connected to said piston, and a separate fluid pressure system including a dash pot having a piston arranged in the path of said stop to establish a back pressure and produce a slow feed of the wheel, means for adjustably regulating the effective back pressure in said separate system, and means for effecting the reverse movement of said dash pot piston independently of the feeding mechanism.

7. In a grinding machine, feeding mechanism, a fluid pressure cylinder and piston, a

rack reciprocated thereby for operating the feeding mechanism, a stop carried by the arranged to be latched under tension by the operator to hold said valve open, and a trip actuated by said calipering device to release the latch so that the valve will close and stop the feeding movement when the work reaches a predetermined size.

9. A grinding machine having a base, a work support, a transversely movable wheel slide, a rotatable grinding wheel on said slide, a feed mechanism including a nut and screw to move the slide and wheel towards and from the work, a fluid pressure device to rotate said feed screw and feed the wheel continuously into the work, and a caliper mechanism arranged to engage the work piece and to control said fluid pressure mechanism and wheel feed to stop the feed when the work reaches a predetermined size.

10. In a grinding machine having a base, a work support, a transversely movable wheel slide, a rotatable grinding wheel on said slide, a feed mechanism to move the slide and wheel towards and from the work, a fluid pressure device to actuate said feed mechanism, a calipering device arranged to engage the work piece, and two valves responsive to movement of said calipering device which are arranged to successively stop the infeed and to move the wheel rearwardly to an inoperative position.

11. A feeding mechanism for grinding machines having a work support and'a rotatable wheel comprising a nut and screw mechanism to feed the grinding wheel toward and from the work, a rack bar arranged to turn said feed screw in either direction, a fluid pressure piston and cylinder mechanism op-- eratively connected to move said rack in either direction, a caliper arranged to engage the periphery of a work piece, and a valvemechanism actuated by said caliper to stop and reverse the flow of fluid and-thereby remove the wheel from the work when the work has reached a predetermined size. I

12. A grinding machine having a base, a work support, a transversely movable wheel slide, a rotatable grinding wheel on said slide, a feed mechanism including a feed screw and nut to move the slide and wheel towards and from the work, means including a piston and cylinder mechanism to rotate said feed screw and continuously feed the grinding .wheel rapidly into the work, and a calipering device including a valve which is arranged to be actuated when the work reaches a predetermined size to reverse the flow of fluid in the cylinder and remove the grinding wheel from an operating position.

13. In a grinding machine having a rotatable grinding wheel and a work support, a feeding mechanism for said wheel, a fluid pressure cylinder and piston for actuating said mechanism, a pair of valves arranged adjacent each other, one of said valves being movable to stop the movement of the feeding mechanism in one direction, the other valve being arranged for movement thereafter to reverse the direction of flow of said fluid pressure to reverse the feeding movement, and a caliper device actuated to initiate the movement of said valves one after the other.

14. A grinding machine comprising a work support and a grinding wheel which are relatively movable towards and from each other to effect a grinding operation, a feedin mechanism therefor, a calipering device liaving a member movable in response to a decrease in size of the work, a fluid pressure actuated mechanism including a cylinder and piston operatively connected to actuate said feed mechanism to cause a relative infeed and reverse movement of the Wheel and the work, and means including a control valve responsive to movement of said caliper member effective to control said fluid pressure mechanism and cause the infeed movement to cease when the work has reached a predetermined size and a reverse movement when the work has been ground to a final size.

15. A grinding machine comprisin a work support and a grinding wheel w ich are relatively movable towards and from each other to effect a grinding operation, fluid pressure actuated mechanism including a valve control device to cause a relative infeed and a reverse movement of the wheel and the work, a caliper device having a movable member engageable with the work and means responsive to movement of the caliper member which actuate the valve control device and cause the infeed movement to cease when the work has been ground to a predetermined size and a reverse movement when the work has been reduced further to its final size.

16. A grinding machine comprising a work support, a grinding wheel movable towards and from the work, a fluid pressure actuated mechanism to move the wheel forward for a grindin operation and rearwardly from the wor two valves for controlling said mechanism, one being connect-- ed to stop the infeed of thecwheel and the other to cause the wheel to move rearwardly, a caliper device including a member movable in response to a decrease in size of the work and means responsive to movement of said caliper member which is connected to actuate said valves successively when the work reaches a predetermined finished size,

and means including a second valve controlled thereafter by said caliper mechanism to move the grinding wheel rearwardly after ithas been ground to a predetermined size.

18. A grinding machine comprisin a work support and a grinding wheel, a uid pressure actuated feed mechanism to move the wheel towards and from the work, a caliper engaging the work, two valve mechanisms controlling the feed mechanism, one connected to stop the infeed of the wheel and the other to cause the wheel to move rearwardly, an actuating mechanism for each valve, and connections between said caliper and the valve actuating mechanisms which cause the latter to act successively.

19. A grinding machinehaving a base, a work support, a transversely movable wheel slide, a rotatable grinding wheel on said slide, a feed mechanism to move the slide and wheel towards and from the work, means including a piston and cylinder mechanism to actuate said feeding mechanism and feed the grinding wheel rapidly into the work, a secondary cylinder and piston arranged to serve as a dash-pot to slow down the feeding movement of the grinding wheel when the grinding wheel approaches the surface of the work, a valve in said secondary cylinder arranged to adjust the'slow feeding movement for the grinding wheel, and a calipering device including-a'valve which is arranged to be actuated when the work reaches a predetermined size to reverse the flow of fluid in the cylinder and remove the grinding wheel from an operating position. 20. A grinding machine having a base, a

Work support, a transversely movable wheel,

slide, a rotatable grinding wheel on said slide, a rotatable feed mechanism to move the slide towards and from the work, a fluid pressure device including a piston and cylinder which are operatively connected to move a rack bar to turn the feed mechanism and feed the grinding wheel rapidly towards the work, a secondary cylinder and piston arranged to slow down the feeding movement of the grinding wheel at a predetermined point, a calipering device arranged to engage the work piece, anda valve actuated by said caliper to reverse the flow of fluid to said first cylinder and move the wheel rearwardly when the work has been ground to a predetermined size.

Signed at Worcester, Mass, this 13th day of March 1929.

WARREN F. FRASER.